The invention concerns an evaporator flask for a rotary evaporator. These types various rotary evaporators are commonly known and in use. DE-A-25 34 446, for example, shows such a rotary evaporator with a vapor duct pipe for transfer of the vapor through a holding and drive device. The holding and drive device supports the flask and transmits the rotational motion. Since the cooler or condenser are arranged to be stationary, and the flask, on the other hand, rotates, a shaft seal with a sealing lip is anticipated, which engages in the vapour duct pipe.
EP-A1-504 099 shows a comparable arrangement with a two part duct pipe.
With rotary evaporators, in practice round flasks or pear-shaped flasks are almost exclusively used. Regarding the partial vacuum prevailing in the flask, the mechanical loading from the freely projecting, inclined flange attachment, and regarding adequate formation of a thin film, these types of round or pear-shaped flasks are considered by the expert as being the only alternative for use in connection with rotary evaporators. The disadvantages dictated by the geometry of round or pear-shaped flasks, such as, for example, difficult cleaning and the risk of foaming over, have for decades been accepted as unavoidable.